Short wave radio communication system



De@ 15, 1935- G. A. MATHIEU 72,064,481

SHORT WAVE RADIO COMMUNICATION SYSTEM Filed 061;. 25, 1932 8 Sheets-Sheet l INVENTOR- l @ASTON AoEuN MATHlEu ATTORN EY- Dec. 15, 1936.

G. A. vMATHIEU SHORT .WAVE RADIO COMMUNICATION SYSTEM Filed Oct. 25, 1932 8 Sheets-Sheet 2 ATTORNEY- Dec. 15, 1936. G. A. MATHIEU 2,064,481 *i SHORT WAVE RADIO COMMUNICATION SYSTEM Filed Oct. 25, 1932 8 Sheets-Sheet 5 ,V5 s V4 E E nn. un.

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ANTENNA INVENTOR- GASTON DELIN MATHIEU iii BYWSQM ATroRNEY- Dec. 15, 1936.

G. A. MATHIEU SHORT WAVE RADIO COMMUNICATION SYSTEM Filed Oct. 25, 1932 8 Sheets-Sheet 4 .wir

Il `E INVENTOR- GASTON ADELIN MATHIEU ATTORNEY- Dc. l5, 1936. G. A. MATHIEU 2,054,481

SHORT WAVERADIO COMMUNICATION SYSTEM Filed oct. 25, 1932 e sheets-sneu 5 ,02,475 /zffw IlEnf/fbg ATTORNEY- SHORT WAVE RADIO COMMUNICATION SYSTEM Filed Oct. 25, 1932 8 Sheets-SheerI 7 INVENTOR- GASTON ADEUN MATHIEU ATTORNEY- D. 15, 193e. G, A MATWEU O 2,064,481

SHOR1 I WAVE RADIO COMMUNICATION SYSTEM Filed Oct. 25, 1932 8 Sheets-Sheet 8 INVENTOR- GASTON ADELIN MATHIEU BY lf@ ATTOR N EY- Patented Dec. l5, 1936 .sont

giitifiti SHORT WAVE RADIO C i i? 'A SYSTEM Application October 25, 1932, Serial No. 639,462

In Great Britain November 5, 1931 11 Claims.

This invention relates to short wave radio communication systems and thermionic valve constructions for use therein. More particularly though not exclusively the invention relates to very short wave systems operating on the socalled Barkhausen-Kurz principle wherein as is well known a thermionic valve is utilized as an oscillator by making the control electrode highly positive with regard to the cathode and maintaining the anode at a potential which is the same as the cathode potential or which may be slightly positive or slightly negative with respect thereto.

As will readily be appreciated many practical diiculties are experienced in and in connection with ultra short wave transmitters of this type, two oi the main diiiiculties being that of transferring the oscillatory energy within the valve or valves employed, to an antenna in an eiiicient manner and radiating the very short wave energy efficiently from the antenna. A further diiiiculty lies in the actual construction of the transmitter, this diiculty arising by reason of the very small permissible dimensions of the electrodes employed to produce the very short wave lengths. A still further diiiiculty arises by reason of the fact that it is practically impossible or at any rate exceedingly diflicult to earth such an ultra short wave transmitter or receiver satisfactorily since in practice an earth wire, which is of negligible lengthas compared to the very short working wave length, is diiiicult if not impossible to obtain. The last mentioned diiiiculty has in part been met by the employment of the dipole or doublet type of antenna, the said antenna being connected to the thermionic oscillatory system through a Lecher wire system one half of the antenna being joined to the plate and the other to the grid point in each case via the Lecher wires. Even with this arrangement, however, difiiculties arise because the phasing of the antenna currents is not usually perfect since in a transmitter the grid side of the doublet has to perform most of the useful work, while in a receiver the heavier share of the work is performed by the anode side of the doublet.

So far as the construction of ultra short wave aerial systems of the doublet type is concerned attention is directed to my United Statesl Patent No. 2,049,070, granted July 28, 1936, which describes an invention according to which a skeleton type aerial comprises a plurality of rod-like radiators or aerial members supported solely substantially at theiry middle points (where voltage nodes occur) the ends of the rod-like radiators being free in space.

The present invention and the invention contained in my United States Patent, supra, above referred to, are both concerned with the finding of 5 a practical commercial applicable solution of the difliculties arising in Ultra short wave transmitting and receiving systems and the two inventions in question may with considerable advantage be employed in combination.

The invention is illustrated in the accompanying drawings.

Figur-e 1 illustrates diagrammatically one form of transmitting circuit;

Figure 2 shows a preferred practical arrangement whereby high tension supply may be fed to the grids of the valves in a transmitter in accordance with this invention;

Figure 3 is illustrative of an alternative method of feeding high tension to the grids of the valves; 2O

Figures 4 and 4a, illustrate a suitable constructional arrangement of valves for use in a. transmitter as illustrated diagrammatically in Figure 1;

Figure 5 shows an arrangement wherein fila- 5 ment connecting Lecher wires are employed to couple together two push-pull oscillators in synchronism and in isochronism or any other desired phase relationship;

Figure 6 shows an arrangement in which four u oscillators in synchronism are employed;

Figure 7 shows in diagrammatic detail a preferred form of receiver; while Figures 8, 8a and 8b are illustrative of a method of combining a plurality of doublets in a multiple aerial reflector system.

Figure 9 illustrates a preferred and somewhatV modified form of the transmitter shown in Figure 1 of the drawings;

Figure 10 shows in elevation, and Figure 11 in o end view, a construction of the valve in which the difliculty of the introduction of small extra length wires in the plate circuit is avoided;

Figure 12 shows schematically a pair of valves arranged to operate as the valves V1, V2 of the transmitter, as illustrated in Figure l of the drawings;

Figure 13 shows an efficient arrangement of aerial and associated reflectors wherein one aerial is located in front of and centrally between two reflectors;

Figure 14 shows a preferred aerial arrangement of combined transmitter and receiver station;

Figure 15 shows a receiver corresponding close- 55 ly in general arrangement to the transmitter of Figure 9;

Figure 16 shows an arrangement wherein one valve of a pair has been replaced by its equivalent network;

Figure 17 shows a keying system for an oscillator arrangement such as Figure 1;

Figure 18 shows the application of a system like Figure 17 to a receiver and transmitter arrangement;

Figure 19 illustrates a further arrangement wherein key clicks are avoided in the special manner described hereinafter.

Referring to Figure 1 of the drawings the radiating element consists of a doublet antenna A constituted by a copper or silvered copper rod preferably terminated by discs b1 and b2 which serve to reduce the damping of the doublet and to ensure a more uniform distribution of current than would otherwise be possible. The members b1 and b2 may, if desired, be in line with rods and need not necessarily be constituted by circular discs. The doublet is energized from valves V1 V2 constituting a push-pull connected oscillator. The two sides or halves of the radiating doublet are connected to the grids of the valves, as shown through the two wires of a Lecher wire feeder, ,f1 f2 the distances between the connection points of these feeder wires with the doublet and the centre point of said doublet being so chosen that the surge impedance of the feeder f1 f2 is matched. This surge impedance of course depends, inter alia, upon the diameter and distance apart of the component wires of the feeder f1 f2 and if maximum transfer of energy from the Valves to the doublet is to be obtained this surge impedance must be matched to the valves and to the doublet. The Lecher wire feeder f1 f2 is employed as an impedance transformer to ensure the maximum transfer of energy from the oscillator to the antenna and the said feeder will therefore usually be less than one wave length long. High tension supply to the grids of the valves is applied from a battery or other source Eg through an indicating meter and a variable resistance R1 to the centre point of the doublet. The anodes of the valves V1 V2 are joined together by a very short lead of predetermined and preferably adjustable length (this length in conjunction with the inter-electrode capacity of the anodes of the valves V1 and V2 plays an important part in determining the tuning) and the cathodes are joined by a very short lead as shown in the Figure l now being described. The length of the wire joining the anodes is found to be critical since it is necessary to obtain the correct phase relationship between the high frequency potentials on the two anodes and to ensure that the potentials on the two halves of the dipole shall be exactly 180 out of phase.

When using valves in which the anode connections are brought through the stem with the lament leads the two short leads may be constituted each by a meta-l plate the two plates being arranged clcse to one another and underneath the valve sockets or mountings, in such manner that they together constitute not merely the short leads but also a condenser d. g is a copper tube which is soldered or otherwise suitably fixed, to the filament connecting plate of the condensed d and is employed as a support for the whole or part of the transmitter the said tube also being employed to contain any insulated wire or wires leading to the electrodes of the Valves for applying direct current potentials thereto. This method of housing direct current feeding wires, results in effective shielding and also protects the wires from being moved about by wind or similar extraneous forces.

The other ends of the cathodes are prolonged into the Lecher wires f3 f4 the Lecher wires being adjusted to be suitable for the working wave length. The filaments are heated from batteries Ef; and Ef2 (which batteries may be if desired constituted by a single battery) earthed at one side and connected on the other through variable resistances R2 R3 to movable tapping points upon the Lecher wires. The filament Lecher wires are prolonged beyond the supply points for approximately one quarter of the working wave length so as to ensure the existence of a current loop at that point. Alternatively the necessity for prolonging the Lecher wires may be avoided by connecting a comparatively large condenser across the supply points. The tube gis earthed through a variable tapping point as shown.

It will be appreciated that the arrangement of the circuit for the filaments results in their being supplied with energy at a nodal point of potential.

The anodes of the valves V1 V2 are connected through a lead h and a suitable indicating instrument to one end of the secondary of a transformer Tri the other end of the secondary being connected through a battery Ep to earth. Modulating potentials are applied to the primary of the transformer Tf1.

A preferred arrangement for feeding high tension supply to the grids of the Valves is illustrated in Figure 2 of the drawings in which figure the doublet A is shown as supporte-d by a metal pillar a fixed to an insulating block b which is itself supported upon a copper tube C which serves to support the antenna system within the refiector system. The block b may be slid along the tube C and clamped in any position for the purpose of moving the doublet A into the correct focal line position, assuming the reflector (not shown) to be a parabolic reflector as described in my United States patent, supra. The high tension conductor (shown schematically for convenience in drawing at the top of Figure l) for supplying grid potential is actually passed up through the tube g, from which it is insulated, and on emerging from the said tube g (Figure 1) is continued up through the plates of the condenser d (the two plates of the condenser d are formed with apertures to permit the passage of the insulated high tension wire) and then through the copper tube C of Figure 2 whence it is connected as shown to the supporting pillar a. The high tension oircuit is thence completed via the doublet antenna itself and the feeder wires f1 f2 as represented diagrammatically in the said Figure 1. In this manner mechanical rigidity and a high degree of screening is obtained. In the alternative arrangement of grid high tension feed supply illustrated in Figure 3 the high tension supply is taken to a point between two cholres interposed in a lead connecting the grids of the valves together, and condensers ci c2 are inserted, as shown, in the feeder wires f1 f2. This connection system permits of the electrical centre of the doublet being arranged as shown in the said Figure 3 and of the insertion of a thermo-couple or radio frequency meter in the centre point of the doublet to facilitate correct adjustment of the transmitter. As will be obvious, the positions of the condensers ci c2 and radio frequency blocking chokes are capable of considerable variation from that shown in the Figure 3 now being described.

The doublet antenna with its insert thermocouple or other indicating meter and a. considerable portion of the feeder f1 f2 may be mounted within a glass or other suitable container to protect it from the weather, and the remainder of the transmitter may be enclosed in a weather proof box into which the glass container or the feeder alone fits with a moisture proof insulating joint. The screening box should, of course, be so constructed and arranged that it does not give rise to interference eiects by reflection of energy.

Alternatively, in place of using an enclosing grotective box the antenna and feeder may be coated with a layer of cellulose or similar protecting varnish or enamel. It is also of advantage to provide such a protective coating to the reflector associated with the system.

Figure 4 illustrates in perspective elevation, and Figure la in schematic sectional plan taken in the plane of the filaments, one possible form of construction and arrangement of the valves V1 V2 which valves should be arranged side by side and as shown in the said Figure e so that the leads from each electrode or a valve may be made equal to the corresponding leads from the other Valve, the arrangement of the electrodes and leads being symmetrical about a plane equidistant between the two valves. It will be seen that the valves are not alike and are not interchangeable in position ii best results are to be obtained, i. e. if the symmetricalV arrangement shown in the said Figures 4 and la is to be maintained. Starting from this central plane and reading outwards there are rst the plate supports PS, then the leads to the rear ends RE of the filaments (i. e. the ends furthest from an observer in Figure 4) then the leads to the high potential ends HP of the laments and lastly the grid supports GS. One of the plate supports PS of each valve is continued and connected to leading out wires PSW which leave the valves near the filament leads REW and HPW the above mentioned relative positions being maintained. The plates are supported at each end by insulated supports PS only one of which, namely that near the low potential end RE of the filament, is continued electrically to form the connecting lead PSW. So long as the symmetrical arrangement is accurately maintained, reversal of the lament leads position is` not of much importance, and of course the low potential end of each la.- ment must be earthed.

The grid supports GS (as will be seen there are two) are also insulated from each other the grid connection GSW in each case being brought out through the valve envelope from the end of the grid adjacent the high potential end HP of the filament. As will be seen two grid supports and also the two plate supports are insulated from one another by glass beads so that neither the plate nor the grid of either valve has its ends connecter. together through these supports. For reasons described later, the grid connections may be brought out on each side of the valve i. e. one lead from each end of the grid.

Alternatively, the separate support and lead for the high potential end of the lament may be provided at the bottom of each valve, it being necessary to arrange that the capacities between the high potential ends of the filaments and their leading out wires and the plates and low potential ends of the laments should be very small.

For wave lengths of say between 30 and 100 centimeters two separate valves may economically be employed, but for shorter wave lengths it will possibly be found necessary to locate the electrode system constituting the two valves side by side in one envelope so as to avoid the difculty of obtaining the very short interconnections necessary with such very short wave lengths.

Numerous modifications as to the manner in which modulation is eiected may be made. In the case of Figure l already described, modulation is eifected by means of a transformer in `series with the plate circuit of the valves, this transformer being, of course, of low ohmic resistance in its secondary windings to avoid reducing the power of the transmitter. The amount of modulation power required with this method is very small andthe application of a correct value of negative potential to the plates is an important factor in determining quality.

An alternative method of modulation is by varying the high tension supply to the grids of the valves by means of a powerful amplifier connected through a transformer whose secondary is in series with the supply leads.

Yet another method of eecting modulation is by the application of low frequency push-pull modulation in the plate or grid circuit of the oscillator.

In the former case (i. e. push-pull modulation in the plate circuit) the plate circuit is split and two suitable condensers inserted in series, leads being brought from across these two condensers to the secondary winding of a modulation transformer the high tension supply being, of course, fed to the center point of this winding. In the latter case (i. e. push-pull modulation in the grid circuit) the said grid circuit is analogously arranged by splitting the antenna at its center point and inserting a large condenser or two condensers in series to permit of the insertion of the secondary winding of a push-pull transformer across them, the high tension supply being, of course, fed to the middle point of this winding.

With reference to the circuit illustrated in Figure l, it should be understood that this circuit is quite satisfactorily operative with half the power i. e. it will operate successfully if one of the valves is switched off (or burnt out) or is replaced by the equivalent capacity network as shown in Figure 16. In general, however, maximum output will be required and the two valves in push-pull should be employed.

In Figure 16 the valve V1 of Figure lhas been replaced by its equivalent network. The lament battery Efi has been removed as it is not required. Capacities K1, K2 and K3 are equivalent to the anode to filament, anode to grid, and grid to lament capacities, respectively, in the valve. Resistances S1 and S2 are equivalent to the effective resistances between the anode to filament and grid to lament circuits.

Obviously, reception can be achieved by arrangements as already described by providing means for listening in the modulating circuits. It is preferred, however, to employ a special arrangement for receiving, which arrangement will be described later with reference to Figure 7.

Figure 9 of the accompanying drawings illustrates diagrammatically and schematically a preferred and somewhat modified form of the transmitter shown in Figure l of the drawings.

It will be noted that the arrangement of Figure 9 diiers from that of Figure 1 of the drawings principally in the arrangement of the l'ament circuit and that four main tuning adjustments are provided as indicated at I, 2, 3 and 4. These four adjustments arez-adjustment (1) of the length of the Lecher wire feeder f1 f2 connecting the grids of the valves V1 V2 to the aerial. This adjustment together with adjustment of the distance between the conductors f1 f2 enables the impedance of the feeder constituted by the said conductors to be matched to that of the aerial and the correct terminal conditions obtained.; adjustment (2) of the length of the plate conductors f7 fa; adjustment (3) of the conductors f5 fe from earth to the earthed ends of the filaments; adjustment (ll) of the conductors is f4 to the ends of the laments. The correct conditions of tuning, i. e. the proper lengths of conductors (in terms of the working wave length A) are indicated in Figure 9. As regards the proper lengths of the leads interconnecting the two plates and interconnecting the earthed ends of the filaments those would ordinarily require to be so short that, where separate valves of normal dimensions are employed for the valves V1 V2 the constitution of these interconnecting leads would be practically impossible owing to the fact that the envelopes of the valves cause their physical separation by too great a distance. This difficulty can be avoided by increasing the lengths of these interconnections each by one wave length and bending the added wave length of conductor each back upon itself, hair-pin fashion, as indicated in the accompanying Figure 9 so that the said added wave lengths are non-radiating.

In practice, each Lecher wire or hairpin conductor employed for tuning is arranged in a screened earthed copper tube and this enables the tuning systems to be arranged side by side in a screened box without giving rise to undesired couplings.

The frequency of oscillation generated will depend. upon the tuning, upon the potentials applied to the valves and also upon the dimensions of the plates and grids of the valve. It is found that a fairly wide range of frequencies can be obtained with a given suitable type of valve in a transmitter as illustrated in the accompanying Figure 1 and in fact a frequency range of 25 X 10 cycles has been obtained. Tuning adjustments (2) and (3) are very critical in determining the frequency generated while tuning adjustments (l) and. (4) determine the efficiency of the transfer of energy from the valves to the aerial. The shortest wave length which can be obtained from any particular transmitter is in practice that which is obtained when the proper length of the conductor between the two plates necessary to tune to that wave length is the smallest practicable length. For shorter wave lengths valves with smaller electrodes and capable of generating at lower grid negative voltages the limiting frequency obtained with the larger valves must be used. In practice, valves having plates 20 mm. long and 1l min. diameter have been used for the wave length range I0-45 cms. (with 30() volts positive grid potential for 50 cms.) while valves with plates 15 mm. long and 9 min. in diameter have been used for lthe range Bil-35 cms. (with 175 volts grid positive for 5) cms).

Although the forni of valve shown in Figures 4 and la is a form which can be used, it is found diflicult to obtain satisfactory results from an ultra short wave transmitter as described in the said specification if the valves therein employed are of this form and are fitted with sockets.

The practical necessity to avoid the use of sockets is an obvious serious disadvantage leading to considerable delays in the event of a valve burning out, and moreover involving the risk of upsetting some of the critical adjustments of the circuit in question.

The difficulties met with in attempting to fit valves, as shown in Figures 4 and la with sockets are due to the fact that the use of such sockets in these valves involves the introduction of, a small extra. length of wire in the plate lead, this extra length although quite small being sufficient to prevent the valves from oscillating.

Figure l0 shows in elevation, and Figure ll in end view, one construction of valve in which the above mentioned practical difficulty is avoided, and Figure l2 shows schematically a pair of valves arranged to operate as the valves V1 V2 of a transmitter as illustrated in Figure 1 of the drawings. It will be observed that the principal difference between the arrangement of valve iilustrated in Figures ll) to l2 inclusive and that illustrated in Figures 4 and ea of the drawings is that the plate of the valve is completely insulated frorn the socket, the lead to the plate being brought through the glass bulb. In Figures l() to 12 now being described, P represents the plates, G the grids and F the lanients, the plate lead PL being brought through the glass envelope of the valve shown. As will be seen, the valve sockets are so arranged that the plates do not lie parallel to one another and so the conductors leading to the low potential ends of the plates are brought close together. These conductors indicated at PL1 are either cut off to the correct length (which may be found experimentally) and joined together or, as illustrated in Figure l2, are connected together through a sliding connector arrangement whereby the effective length of lead between the plate P of one valve and the plate P of the other can be conveniently adjusted. The grid leads are continued into the Locher wires f1 f2 corresponding to the Lecher wires f1 f2 of Figure l of the drawings.

The necessity for distinction in arrangement of the valves between the high and low potential ends of the electrodes and the need for maintaining symmetry apply also to whatever type of valve is employed.

While the length of the connecting leads between the two valves is very critical once it has been determined, it is possible to increase it by integral multiples of half wave lengths and still obtain the benefit of the invention. This allows the valves to be spaced apart more than when the shortest length of connection is used and further allows the envelopes of the valves to be made of larger size, an advantage from the point of view of heat dissipation.

The same types of valve and circuits above described are suitable for receiving purposes. Microphonie noises can be substantially eliminated by mounting the envelopes of the receiving valves in rubber sponge blocks.

Figure 5 shows two push-pull oscillators consisting of valves V1 V 2 V3 V4 coupled together by lament Lecher Wires. If the extremities of the filament Lecher wire systems remote from the valves are connected directly together as shown in the said Figure 5 and if the said systems are of the correct length, perfect irl-phase excitation of the two oscillators can be obtained. Since, of course, the frequency generated by the oscillators depends on small Variations in geometric construction as well as on supply potentials, it is necessary to adjust one oscillator until its wave length closely approaches that of the other, when the two will pull in step. In practice, this adjustment is best carried out by varying the lilament current of each valve separately and keeping the other supply potentials constant. In order to facilitate this, blocking condensers C1 C2 Cs C4 are inserted in the iilament Lecher wires as shown, i. e. in that portion of. the system which is employed to couple the oscillators together. In Figure 5 the potential distribution (theoretical) has been indicated by broken lines. In practice however, the distribution curve probably continues and falls to zero at the earth point. The actual effect obtained is, however, complex since a portion of the high frequency current passes through the capacity formed by the leads to the valves at the point where they aresealed into the glass. Figure 5, however, is illustrative of the manner in which energy which would otherwise be wasted in the filament Lecher wire system may be utilized for linking together two or more transmitters.

Another method of coupling transmitters in synchronism and isochronism o-r in any other phase relation is to prolong the grid circuit of the valves in a direction opposite from the antenna. For this, of course, connection must be made to both ends of the grids of, each valve, this connection being made through the glass envelopes, as previously explained. In this Way the grids are in effect prolonged on both sides of the valves into Lecher wire systems, and the rear Lecher wire systems of two or more transmitters are joined together at predetermined points so as to achieve a predetermined phase relationship of coupling.

In yet another method of coupling two transmitters in synchronism and isochronism or in any other desired phase relationship, the grid leads are coupled at a point between the grids of the two valves and the antenna of each transmitter. The arrangement is similar to that showny in the Figure 5 just described, but the use of condensers at each end of the coupling wires is not necessary since the two systems will normally be fed with grid current at the same potential.

In carrying out the present invention, Lecher wire systems to the antenna or for the filaments or for grid couplings may be wholly or in part replaced by coils of the required equivalent electrical dimensions in order to reduce space where required. Such coils should, of course, be so designed that the potential distribution simulates as closely as possible that which obtains in the Lecher wires.

In addition the Lecher wire systems may be prolonged on both sides of the valves and antennae may be connected at each end, or alternatively, one end may be short circuited at a point so chosen as to reflect back to the antenna, with the correct predetermined phase angle, any energy which may be radiated from the valves themselves.

Figure 6 shows a modification or development of the arrangement illustrated in Figure 5, in which four transmitters are coupled together. In the said Figure 6, as in the said Figure 5, the circuits are not shown in full, but only insofar is necessary to illustrate a method of coupling. Obviously the invention is not limited to coupling two or four transmitters together, the systems of the said Figures 5 and 6 being capable of extension almost without limit. Obviously the doublets in the separate transmitters which are coupled together in the said Figures 5 and 6 may be arranged in any required positions to secure requireddirectional effects. Alternatively, the circuits may be adjusted so that the doublets oscillate with a denite predetermined phase difference for securing desired directional effects. Various methods of combining doublets will be described with reference to Figures 8, 8o and 8b and with reference to' Figures 13 and 14 of the accompanying drawings.

Figure 7 shows one. form of receiver, the construction of which will, it is thought, be fairly obvious from the description already given with reference to Figure 1 of this specification. Referring to the said Figure 7, A is a doublet antenna which may be an exact duplicate of that employed at the cooperating transmitter and arranged with discs as illustrated, said discs being preferably adjustable along their corresponding antenna halves. (The provision of adjustably mounted discs is also to be recommended in transmitter aerials.) The lengths of the feeders fi, fz, have an important influence on the tuning of the receiver and may be easily made adjustable by constituting them by copper rods adjustable within copper tubes as indicated. Maximum signal strength will be obtained when the feeder length, the antenna length, and the position of the contact points of the feeders on the antenna are such as to give maximum response to the incoming wave and to provide maximum transfer of energy from the antenna to the valves.

It will be noted in the Figure 7 now being described that the plates of the valves Vi and Vz are connected to the doublet antenna, thegrids being joined with short leads of predetermined and preferably adjustable length (see preceding description With regard to the corresponding leads in the transmitter). It has been found that this arrangement gives very good sensitivity. Accurate tuning is obtainable by alteration of the .potentials applied to the valve electrodes, these adjustments being eifected in' obvious manner by the potentiometer and other variable resistance devices illustrated in Figure 7. For telephonic reception, very ne and accurate control of both lament and plate voltages is necessary, and many combinations of potential adjustments are possible for giving good results.

It has been found that to detect properly, the plates of the valves Vi and V2 should be maintained at a positive potential slightly in excess of the filament voltage drop. In this condition the valves do not easily oscillate. If an auxiliary oscillator (of widely adjustable frequency) be provided and employed to superimpose an E. M. F. on the plates of the valves its effect will be to bring the valves rapidly and alternately to the condition (positive plate potential) for detection and to the condition (negative plate potential) for oscillation, and super-regenerative reception can therefore be accomplished. I-Iowever, such super-regeneration is not necessary and quite good results can be obtained without a local oscillator and with the valves biased to the detecting condition. The principal disadvantages in dispensing with super-regeneration are reduced sensitivity andra necessity for somewhat more critical adjustment.

The audio output of the receiver proper (that is from the valves V1 and `Vz) is choke-capacity coupled as shown to a succeeding valve Vs arranged in the ordinary way. Obviously instead of employing the arrangement shown for the supply of potential to the anodes of the valves V1, V'z,

thisv supply may be made through the doublet 55 ment of echo suppressor may be arranged in conin a manner analogous to that already described with reference to a transmitter and illustrated in Figure 2. In such an arrangement the anode supply lead is run through a copper tube connected to the center point of the grid connection or to earth and placed as nearly as possible exactly midway between the feeders f'i, fz, so that the system is stabilized when approaching the point o oscillation.

As in the case of a transmitter, one of the valves Vi or V2 may be replaced by an equivalent capacity network and receivers may be coupled together in a manner analogous to those already` described with reference to the coupling together of transmitters.

Figure 15 of the accompanying drawings shows a receiver which as will be seen corresponds closely in general arrangement to the transmitter shown in the accompanying Figure 9. Parts in the accompanying Figure 'i5 corresponding to parts in the accompanying Figure 9 are indicated by like reference numerals but with an affixed tick. As will be seen one main difference is that the plates oi the valves V1 V2 are connected to the aerial A', the grids being coupled via condensers C4 C5 to the primary of a transformer Tr whose secondary eeds (preferably through a low pass lter LPF) into a low frequency amplifier (not shown) rli'he condensers C2 C3 C4 C5 and the chokes Cil-I1 CH2 enable separate readings of the D. C. grid currents of the two valves to be taken on the instruments I1 I2. AO is a local oscillator (for super-regeneration) which is variably coupled to the receiver proper as shown while PA 'and RA are an adjustable potentiometer and resistance respectively. The low pass lter eliminates unwanted high frequency due to the oscillator AO.

As in the case of a transmitter where the working wave length is predetermined and fixed, adjustments 3, 4 and I (or 3', li', I as the case may be) may be dispensed with and fixed values instead of variable values provided.

Referring now to Figure S this shows three doublets IA, 2A and 3A, each having terminating discs which are also employed to couple the doublets together. The doublet IA is connected to a thermo-couple or other rectier and indicating meter (not shown) to facilitate adjustment to the correct wave length. The doublet 2A is the transmitter doublet while the doublet 3A is a receiver doublet the connections for the transmitter and receiver being represented by TTR and RCR respectively. Any known arrangenection with an installation embodying three doublets as illustrated in Figure 8 now in question, and with the use of a suitable echo suppressor duplex working with a single reiiector for both receiving and transmitting is quite practicable.

Figure 8a is intended to represent the dipole arrangement of a double transmitter consisting of two transmitters coupled together, for example, as illustrated in Figure 5, a third doublet IA for connection to a meter being interposed between the two transmitting doublets 2A. The doublet IA which may be referred to as a wave meter doublet by reason of the purpose of its provision, maybe made to" be very sharp in tuning by employing larger discs than are employed on the transmitter doublets, there being, of course, a corresponding reduction in the length of the dipole or doublet between the discs.

The reason for reducing the length of the Wave meter doublet and for increasing the diameter oi the discs is that the damping and consequently the absorption of energy, are considerably reduced thereby, while the current at the center o' the doublet is increased. This enables a larger instrument reading to be obtained, thus facilitating detection of changes of amplitude in the transmitter carrier. Moreover, since reduction of damping sharpens the tuning of the system, the advantage is obtained that the instrument shows not only the amount of the power being radiated but also whether it is being radiated at the correct wave length. Since the power absorbed by the wave meter doublet is reduced to a minimum it does not materially affect the amount of power radiated, and, when arranged as shown in Figure 8a, may actually assist by increasing the effective length of the antenna proper.

In connection with the provision of these wave meter doublets, it may urther be noted that the power absorbed by them (which is reduced to a minimum) assists in p-roducing a more uniform current distribution at the focus of the reiiector.

In another arrangement the wave meter doublet is mounted in front of or just inside the reflectors.

Figure 8b represents an installation comprising two coupled transmitter doublets 2A, each of which is coupled to a wave meter doublet IA. One of these wave meter doublets may, of course, be replaced by a receiving doublet.

Instead of arranging the aerial and associated reflectors as represented schematically in Figures 8, 8a and 8b just described, considerably better efficiency is obtained by using one aerial in front of and centrally between two reiiectors as shown in the accompanying Figure 13. A preferred arrangement of combined transmitting and receiving station is shown schematically in the accornpanying Figure 14 in which I A is a receiver doublet and 2A are transmitting doublets.

Throughout Figures 8, 8a and 8b and the accompanying Figures 13 and 14, the lines marked RFR represent the central wire of the paraboles forming the reflector.

In the transmitting system shown for example in Figure 1 it is possible without detriment to add a comparatively large value or" additional ohmic resistance in series in the plate circuit of the oscillator valves if there is also provided in series with the said plate circuit a source of voltage which serves exactly to balance the voltage drop set up across the terminals of the added ohmic resistance due to the oscillating D. C. rectied compo-nent passing therethrough, and this fact may be utilized to provide a convenient means for keying the oscillator.

Such a keying system is illustrated in Figure 17. Referring to this figure the valves VTi and VT2 correspond to the valve V1 V2 illustrated in Figure 1 of the drawings, and as will be seen there is inserted in the anode circuit to said valves an additional resistance R and a compensating battery EC, the battery compensating for the oscillating D. C. rectified component of voltage appearing across the terminals of the resistance Keying of the oscillator is accomplished by switching in and out the resistance R or short circuiting a part thereof, or, as in the arrangement actually illustrated, by providing a by-pass resistance which is controlled by the keying means, or by altering in some other way the voltage drop occurring down the resistance R. This by-pass resistance is constituted by a thermionic valve KV whose grid circuit is controlled by the keying means. During (say) marking, the

bias applied to the grid circuit of the valve KV is sufficiently negative to prevent any flow of plate current so that in these circumstances the valve KV passes substantially no current. For spacing, however, the bias on the grid of the valve KV is made less negative so that the said valve draws current and in consequence the anode potential applied to the valves VT1 and VTz is changed, the change being of suilcient magnitude to determine whether the valves VT1 and VTi oscillate or not. An arrangement as shown in the Figure 17 now being described can be readily adapted to a. so-called two-way blocking system for telephony. in such systems, of course, the receiver is required to be rendered inoperative when transmission is being effected and the transmitter rendered inoperative when receiving is occurring and in applying the arrangement of the said Figure 17 to such a system the keying means which in the said Figure 17 control the grid circuit of the valve KV are replaced by appropriate means actuated in dependence upon received signals so that when signals are being received the transmitter is rendered inoperative.

The application of the circuit of the Figure 17 just described to such a system is broadly and schematically represented in Figure 18 in which gure M represents a microphone which is transformer coupled to an amplifier valve AV the secondary of the transformer being shunted by a control potentiometer. Amplied o-utput from the valve AV is coupled to the winding W2 of a transformer having a secondary winding W1 in the plate circuit of the valves V'.T.`1` and VT2. In series with the winding W1 is the resistance R and source cf potential Ep the valve KV being as before shunted across the resistance R. A iurther circuit is shunted across said resistance R this further circuit consisting oi a variable resistance R2 and a tertiary winding W3. The tertiary winding is pro-vided in order to prevent key clicks being set up by the alternate stopping and flowing of current into the winding W1 when the valves VT1 V'Iz are changed from the oscillating condition to the non-oscillating condition and vice versa. The winding W3 in series with the adjustable resistance R2 opposes a ux variation which balances the effect of the iiux variation due to the stopping and starting of the oscillator and in this way key clicks are substantially eliminated. The turn ratio of W3 to W1 should be kept high so as to obtain the required value of ampere turns with a very small current thus permitting a large ratio between the resistances R and R2. Figure 19 shows a further arrangement in which another method of avoiding key ciicks is adopted this method consisting in prev venting direct current from passing through the winding W1 of the transformer through which the modulating frequencies are applied to the oscillator valve circuit. In the arrang-ement of the said Figure 19 the resistance R is employed as a low frequency choke the condenser CBC serving as a D. C. blocking and A. C. by-pass condenser.

It will be noted that in all the arrangements illustrated in Figures 17, 18 and 19, the valve KV acts as a limiting device as any excess oi negative biasing ci the said valve over the value required to reduce the plate current thereof to zero is of no eiiect on the Working of the whole arrangement. c

Having thus described my invention, what I claim is:

l. An ultra short wave transmitter system comprising an oscillator consisting of a pair of valves each having cathode, anode and grid electrodes, means for applying relatively high potentials to the grids of said valves relative to their respective cathodes, means for maintaining the anodes of said valves at a low potential relative to their respective grids whereby said valves oscillate on the so-called Barkhaus-en-Kurz principle, a radiating dipole, a tuned conductor system devoid of concentrated reactance conductively connecting the grids of the pair of VValves to the dipole, a tuned conductor system interconnecting the anodes of the valves and an adjustable tunable conductor system in circuit with the cathodes of the valves, the grids of said valves being connected each to a point on either side of the midpoint of the dipole, said points being equal distances from said mid-point and being separated by a distance such that the effective load impedance imposed by the dipole is substantially equal to the surge impedance of the tunable conductor system connecting said dipole to the valve grids.

2. An ultra short wave transmitter system comprising an oscillator consisting of a pair of valves each having cathode, anode and grid electrodes, means for applying relatively high potentials to the grids of said valves relative to their respective cathodes, means for maintaining the anodes of said valves at a low potential relative to their respective grids whereby said valves osciilate on the so-called Barkhausen-Kurz system, a radiating dipole, a tunable conductor system connecting the grids of the pair of valves to the dipole, a tuned conductor system interconnecting the anodes of the valves, a terminal of one cathode being directly connected to a terminal of the other cathode, and the remaining terminals of the cathodes being each connected to a conductor, said conductors extending away from said cathodes parallel to each other, and means for supplying heating energy for said cathodes connected to leads which are variably adjustable over the lengths of said conductors.

3. An ultra short wave transmitter system 4comprising an oscillator consisting of a pair of valves each having cathode, anode and grid electrodes, means for applying relatively high potentials to lthe grids of said valves relative to their respective cathodes, means for maintaining the anodes of said valves at a low potential relative to their respective grids whereby said valves cscillate on the so-called Barkhausen-Kurz systern, a radiating dipole, a tunable shielded conductor system connecting the grids of the pair of valves to the dipole, a tuned conductor system interconnecting the anodes of the valves, a terminal of one cathode being directly connected to a terminal oi the other cathode, and the remaining terminals of the cathodes being each connected toa conductor, said conductors extending away from said catho'des parallel to each other, and means for supplying heating energy for said cathodes connected to leads which are variably adjustable over the lengths of said conductors.

, e. An ultra short wave transmitter system ccmprisingfan oscillator consisting of a pair of valves each having cathode, anode, and grid electrodes, means for applying relatively high potentials to the grids of said valves relative to their respective cathodes, means for maintaining the anodes of said Valves at a lower potential than said grids whereby said valves oscillate on the so-called Barkhausen-Kurz principle, a radiating dipole, a tuned conductor system connecting the grids of the pair of valves to the dipole, a conductor system interconnecting the anodes oi the valves, and a tuned conductor system in circuit with the cathodes of the valves, said cathodes each having two terminals, said last tuned conductor system consisting of conductors individually connected to a terminal of each cathode and grounded at a point in the length thereof, and a tunable connection adjustable with respect to ground connecting the other terminals of the cathodes together.

5. An ultra short wave transmitter system comprising an oscillator consisting of a pair of valves each having anode, cathode, and grid electrodes, means for applying relatively high positive potentials to the grids of said valves relative to their respective cathodes, means for maintaining the anodes of said valves at a much lower potential than said grids whereby said valves oscillate on the so-called Barkhausen- Kurz principle, a radiating dipole, a tuned conductor system connecting the grids of the pair of valves to two junction points on said dipole, a connection between the anodes of the valves and a connection between the cathodes of the valves, said first means for applying relatively high potentials to the grids of said valves comprising a circuit extending from a source of positive potential to the midpoint of the dipole and intermediate the junction points on the dipole connecting with the grids of said valves.

6. An ultra short wave transmitter system comprising an oscillator consisting of a pair of valves each having cathode, anode, and grid electrodes, means for applying relatively high positive potentials to the grids of said valves relative to theirrespective cathodes,rneans for maintaining the anodes of said valves at a much lower potential than said gridswherebysaidvalves oscillate on the so-calledBarkhausen-Kurz principle,a radiating dipole,a iirst conductor system connecting the grids of the pair of valves to the dipole, a second conductor system interconnecting the anodes of the valves, and a third conductor system in circuit with the cathodes of the valves, a capacitor and connections devoid of concentrated reactance extending from said capacitor to a point between the two anodes and a point between the two cathodes.

7. An ultra short wave communication system comprising a pair of oscillator valves each having cathode, anode, and grid electrodes, means for applying relatively high positive potentials t-o the grids of said valves relative to their respective cathodes, means for applying to the anodes of said valves much lower potentials than are applied to said grids whereby said valves runction on the so-called Barkhausen- Kurz principle, a radiating dipole, a first conductor system interconnecting the grids of the pair of valves, a second conductor system interconnecting the anodes of the valves, said first conductor system being connected to said dipole, said second system being connected to high frequency apparatus, a third conductor system circuit with the cathodes of the valves, and a resistance in series in the anode circuit of the valves and a source of potential substantially balancing the voltage drop set up across said resistance in series therewith, and keying means for short circuiting at least a part of said resistance whereby the oscillator system may be lreyed.

3. An ultra short wave transmitter system comprising an oscillator consisting of a pair of valves each having cathode, anode and grid electrodes, means for applying relatively high potentials to the grids of said valves relative totheir respective cathodes, means for maintaining the anodes of said valves at a low potential relative to their respective grids whereby said valves oscillate on the so-called Barkhausen-Kurzsystem, a radiating dipole, a tunable conductor system devoid of concentrated reactance connecting the grids of the pair of valves to the dipole, a conductor system interconnecting the anodes of the valves and an adjustable tunable conductor system devoid of concentrated reactance in circuit with the cathodes of the valves substantially as described.

9. An ultra short wave transmitter system comprising an oscillator consisting of a pair of valves each having cathode, anode and grid electrodes, means for applying relatively high potentials to the grids of said valves relative to their respective cathodes, means for maintaining the anodes of said valves at a low potential relative to their respective grids whereby said valves oscillate on the so-called Barkhausen-Kurz system, a radiating dipole, a tunable conductor system connecting the grids of the pair of valves to the dipole, a conductor system interconnecting the anodes of the valves, a terminal of one cathode being directly connected to a terminal of the other cathode, and the remaining terminals of the cathodes being each connected to a conductor,said conductors extending away from said cathodes parallel to each other, a source of heating energy for said cathodes, and leads adjustable over the lengths of said conductors extending from points intermediate the ends of said conductors to said source, said conductors each having a portion extending beyond the junction point of said leads approximately equal to one-quarter of the length of the operating wave.

10. An ultra short wave transmitter system.

comprising an oscillator consisting of a pair of valves each having cathode, anode and grid electrodes, means for applying relatively high potentials to the grids of said valves relative to their respective cathodes, means for maintaining the anodes of said valves at a low potential relative to their respective grids whereby said valves oscillate on the so-called Barkhausen-Kurz system, a radiating dipole, a tunable conductor system connecting the grids of the pair of valves to the dipole, a conductor system interconnecting the anodes of the valves, a terminal of one cathode being directly connected to a terminal of the other cathode, a condenser connected between said last terminals of said cathodes and said conductor system interconnecting said anodes, and the remaining terminals of the cathodes being each connected to a conductor, said conductors extending away from said cathodes parallel to each other, a source of heating energy for said cathodes, and leads adjustable over the lengths of said conductors extending from points intermediate the ends of said conductors to said source, said conductors each having a portion extending beyond the junction point oi said leads approximately equal to one-quarter of the length of the operating wave.

11. An ultra short wave transmitter system comprising an oscillator consisting of a pair of valves each having anode, cathode, and grid electrodes, means for applying relatively high positive potentials to the grids of said Valves relative to their respective cathodes, means for maintaining the anodes of said valves at a much rst means for applying relatively high potentials to the grids of said Valves comprising a circuit extending from a source of positive potential to a point on the dipole which is intermediate said points on the dipole connecting with the grids of 5 said valves. Y

GASTON ADELIN MATHIEU. 

